This invention relates to a motor that produces a useful, working output based, at least in part, upon the use of a unique arrangement and configuration of permanent magnets. Conventional electric motors employ a changing electrical current to generate an electromagnetic field that interacts with a receptive ferrous material or another magnetic field to create a force and induce movement. The present invention relies upon the energy provided by an electromagnet that is stored in the interacting fields of the stator and rotor permanent magnets for at least a part of its prime motive force.
The motor disclosed herein stores the energy in the interacting magnetic fields of permanent magnets, such as rare earth cobalt magnets. They represent a significant step forward in magnetic energy product and coercive force. Although the composition of these magnets is not a part of the present invention, their properties make the present invention more practical from an economic standpoint. Rare earth cobalt magnets are from twenty to fifty times more resistant to demagnetization than conventional Alnico magnets. As a result, rare earth cobalt magnets may be used in applications for which other magnets were not considered due to their propensity to demagnetize in the presence of a reverse magnetic field of comparable strength.
Based upon the general theories of magnetism, it is believed that each electron in an atom exhibits properties associated with an electric charge spinning on its own axis and producing a small magnetic moment. The sum of these magnetic moments may add collectively to cause the atom to behave as a small magnet. When the atoms are placed into an external magnetic field, each one tends to align with the field, and when the external magnetic field is removed the material usually retains a residual magnetism. If the residual magnetism is strong and difficult to neutralize, i.e. if the magnet has a high coercive force, then the material is commonly known as a "permanent magnet."
In most magnetic materials the magnetic field utilized to align the atomic magnets is sufficient, when reversed in polarity, to disalign or demagnetize the material. This demagnetizing force is referred to as the coercive force H.sub.c and is defined as the magnetizing force required to bring the induction (magnetic flux density or magnetic flux per unit area) to zero in a magnetic material which is in a symmetrically cylically magnetized condition.
For an ordinary Alnico magnet, if a field equal to the coercive force is applied to the magnet to drive its magnetic flux density to zero, and is then removed, the flux will rebound only slightly. The magnet will effectively be demagnetized and remain so until it is remagnetized by another externally generated magnetic field. This happens because the coercive force H.sub.c is nearly the same as the intrinsic coercive force H.sub.ci. The intrinsic coercive force H.sub.ci is the magnetizing force required to bring to zero the intrinsic induction in a magnetic material, or the contributions of all of the elementary atomic magnets.
For a rare earth cobalt magnet, if a field equal to the coercive force H.sub.c is applied to the magnet to drive its magnetic flux density to zero, and is then removed, the flux will rebound almost to its original value. Permanent magnets having this characteristic will commonly have a hysterisis loop exhibiting square loop characteristics. This is due to the fact that rare earth cobalt magnets have values for intrinsic coercive forces H.sub.ci that are several times larger (twenty to fifty times) than the values for ordinary coercive force H.sub.c. Thus, the flux density may be repeatedly driven to zero without adversely affecting the magnet's intrinsic magnetization. This permits the magnet to be used in applications heretofore considered impractical because of the demagnetization that would occur. Although a number of theories have been proposed, it is not yet well known why rare earth cobalt magnets have such properties.
Additional information about the composition of rare earth cobalt magnets and information about their manufacture, characteristics, or uses is readily available in public literature. These magnets have greatly enhanced the operation and power output of the present invention, but they are not an essential part thereof. One may substitute other permanent magnets, such as Alnico magnets, although with less successful results. One may also substitute other sources of magnetic flux, whether generated electrically or by permanent magnets or a combination thereof.
An example of a permanent magnet motor is shown in U.S. Pat. No. 4,151,431 to Johnson, which illustrates that permanent magnets may be used to do useful work. However, it differs from the present invention by using the combined forces of attraction and repulsion, and by using a markedly different mechanical configuration. Moreover, the present invention has a generally uniform magnetic flux density across its stator gap, which the Johnson motor does not have.